1. Field of the Invention
This invention relates to a loudspeaker comprising a movable diaphragm oscillating around a position of rest, a resilient centering device for centering and guiding the movement of the diaphragm, and a magnet system for controlling the movement of the diaphragm. The invention relates specially to woofers which are designed to produce low frequencies.
2. Related Art
In a conventional cone loudspeaker, the guiding of the movable diaphragm is realized by a double mechanical guiding system. This type of guiding system consists of a flexible deformable surround portion that secures the diaphragm to a frame of the loudspeaker, and a spider that guides the oscillation movement of a voice coil positioned in the magnet system and of the diaphragm mounted to the coil. The excursion of the moving system is generally limited by the maximum mechanical deformation of the spider.
Loudspeakers may be divided into several categories. First, there exist loudspeakers designed to produce low frequencies, which are called woofers. In these loudspeakers, the diaphragm is large and has a significant excursion. Additionally, loudspeakers are known that are designed to produce higher frequencies, which are called tweeters. These tweeters comprise diaphragms which oscillate at a smaller range of excursions. Lastly, there also exist loudspeakers designed for producing medium frequencies, which are called mediums or midrange loudspeakers.
In woofers and mediums, a double mechanical guiding system consisting of a surround portion and a resilient centering device (e.g. a spider) is normally used. This double mechanical guiding system is necessary to properly guide the oscillating voice coil and the diaphragm over significant excursions.
In vehicles, audio systems are often provided that include different loudspeakers for different frequency ranges. These loudspeakers often need to be installed in different locations of the vehicle compartment. The loudspeakers may be positioned in a box that needs to be incorporated somewhere in the vehicle. Especially the arrangement of woofer loudspeakers is a challenging task, as the woofer has a large volume. This large volume is necessary to produce the large excursions of the diaphragm that are necessary for producing low frequencies. In the vehicle environment there is always a need to minimize the space needed for the components installed in the vehicle, as the available space inside a vehicle is limited. Accordingly, a need exists to provide a loudspeaker that occupies a minimum volume, but at the same time is able to produce significant excursions of the diaphragm. This need is particularly desirable in the case of woofers.